Control System for Dimmable Windows

ABSTRACT

Electrically dimmable windows for aircraft are powered by energy harvesting devices on-board the aircraft. The harvested energy is stored and used to control the opacity of the windows based on individual window opacity settings selected either by passengers or a cabin attendant. Each window has an associated control circuit that controls the electrical power applied to the window based on the selected opacity setting. The control circuit includes a low energy usage processor that remains in a sleep mode until a change in the opacity setting is detected. Each control circuit may include a radio transceiver that receives control signals from a transmitter operated by the cabin attendant in order to simultaneously remotely control the opacity settings of multiple windows.

TECHNICAL FIELD

This disclosure generally relates to electrically dimmable windows, anddeals more particularly with a system for powering and controllingdimmable windows using energy harvesting devices on-board vehicles, suchas aircraft.

BACKGROUND

Electrically dimmable windows rely on electrical power which is appliedto special materials in the windows in order to change the opacity ofthe windows. Several technologies may be used to construct electricallydimmable windows, including thermotropics, photochromics,photochromatics, liquid crystals, reflective hydrides, suspendedparticle displays and electrochromics.

Electrically dimmable windows have been purposed for use in aircraft inorder to control interior cabin illumination. Previously, passengersused sliding plastic screens covering individual windows in order tocontrol cabin illumination from natural light.

The use of electrically dimmable windows in aircraft increase electricalpower demands for on-board systems, as well as the need for additionalwiring to connect each window with a power source. The need for thisadditional wiring renders it expensive to retrofit existing aircraftwith electrically dimmable windows. Moreover, existing window systems donot allow for central control of all of the windows on an aircraft by apilot or cabin attendant. Accordingly, a cabin attendant must requesteach passenger, typically through a PA announcement, to change windowshade settings during landing, takeoff or during flight, as when it isnecessary to dim the cabin in order to allow passengers to view a movie,or sleep.

Accordingly, there is a need for a dimmable window system for vehiclessuch as aircraft which overcomes the problems discussed above. Thepresent disclosure is intended to satisfy this need.

SUMMARY

A dimmable window system for vehicles such as aircraft is powered byenergy harvesting devices on-board the vehicle, thereby reducingon-board power requirements. The harvested energy is stored aselectrical power in a storage device such as a battery or capacitor. Acontrol circuit controls the opacity of a window using electrical powerdrawn from the storage device. The control circuit may also include aradio receiver which receives window dimming control signals from atransmitter operated by a cabin attendant or pilot, thereby permittingcentral control of all windows on-board the vehicle.

In accordance with one illustrated embodiment, a dimmable window systemis provided, comprising: at least one window having electricallycontrolled opacity; an electrical power storage device for supplyingelectrical power used to control the opacity of the window; and, acontrol circuit coupled with the window and the storage device forcontrolling the opacity of the window. The system may further comprise adevice for harvesting energy and converting the harvested energy toelectrical power. The control circuit may include a power conditioningcircuit for conditioning electrical power from the energy harvestingdevice before the power is stored in the storage device. The electricalpower storage device may be a capacitor or a battery. The controlcircuit may include a window dimming adjustment control for selecting alevel of opacity of each window. The control circuit may further includea microcontroller that periodically awakens from a sleep mode to searchfor window dimming adjustment control signals. The control circuit mayinclude a wireless radio link that allows remote control of the opacityof all windows.

In accordance with another embodiment, a dimmable window system forvehicles is provided, comprising: a plurality of windows on a vehicle,each having electrically controllable opacity; at least one energyharvesting device for harvesting energy on-board the vehicle andgenerating electrical power; storage means for storing electrical powergenerated by the harvesting device; and, a plurality of control circuitsrespectively coupled with the windows, each of the control circuitsbeing coupled with the storage means and operative for controlling theopacity of the associated window using electrical power from the storagemeans. The system may further comprise a controller on-board the vehiclefor generating control signals used to remotely control the opacity ofat least certain of the windows, and a wireless communication linkbetween the controller and the control circuits associated with thewindows, wherein the communication link is operative for deliveringcontrol signals to the control circuits associated with the windows.Each of the control circuits may include a window dimming adjustmentcontrol for selecting a level of opacity of the associated window, and aprocessor responsive to the adjustment control for controlling thedelivery of electrical power from the storage means to the window. Theenergy harvesting device may include, for example, a device forconverting a temperature gradient into electrical power, a device forconverting motion into electrical power, or a device for convertingradiation into electrical power. The device for converting radiationinto electrical power may include a photovoltaic device for convertinglight into electrical power. The control circuits may include amicrocontroller for altering the level of power applied to the window.The wireless data link may include a radio transmitter for transmittingthe control signals, and a radio receiver at each of the windows forreceiving the control signals from the transmitter.

In accordance with another embodiment, a method is provided forcontrolling electrically dimmable windows on-board an aircraft. Themethod comprises the steps of: harvesting energy on-board the aircraft;storing the harvested energy as electrical power; and, using the storedelectrical power to control the opacity of the windows. Energyharvesting may be performed by converting a temperature gradient intoelectrical power, or converting motion into electrical power, orconverting radiation into electrical power. The conversion of radiationinto electrical power may be performed using a photovoltaic device toconvert light into electrical power.

Other features, benefits and advantages of the disclosed embodimentswill become apparent from the following description of embodiments, whenviewed in accordance with the attached drawings and appended claims.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

FIG. 1 is a block diagram illustration showing a control system fordimmable windows in accordance with one embodiment.

FIG. 2 is a block diagram illustration of an alternate embodiment of thecontrol system.

FIG. 3 is a block diagram illustration of another embodiment of thecontrol system.

FIG. 4 is a combined block and schematic illustration showing additionaldetails of a control circuit used in the system shown in FIG. 1.

FIG. 5 is a combined block and schematic illustration showing furtherdetails of the control circuit shown in FIG. 4.

FIG. 6 is a detail schematic illustration of the control circuit.

FIG. 7 is a diagrammatic illustration of a dimmable window withadjustment controls and an opacity sensor.

FIG. 8 is a diagrammatic illustration of a dimmable window having analternate form of adjustment controls.

DETAILED DESCRIPTION

Referring first to FIG. 1, a control system 10 is provided forcontrolling one or more dimmable windows 14 on a vehicle (not shown),such as a commercial aircraft. The dimmable windows 14 are typicallylocated in the fuselage of the aircraft at cabin locations whereillumination from natural light is desired, or where a view to theoutside is desired. The dimmable windows 14 may be constructed using anyof various technologies previously described, including those using anelectrochromatic membrane which changes opacity based on an appliedelectric charge. The electrical charge, and thus the opacity of thewindow, may be varied by applying a voltage of positive or negativepolarity across the membrane. In one embodiment, the window 14 holds itsopacity state when no electric charge is applied to the membrane.Typically, the window 14 increases its opacity when an electricalvoltage is applied of one polarity, and decreases its opacity when anelectrical voltage is applied of the opposite polarity. In effect, thedimmable window 14 may be thought of as a large capacitor whose electriccharge may be varied. In one embodiment, the range of applied voltagesmay be from −1.2V to +1.2V, where −1.2V yields a transparent window, and+1.2V yields an opaque window.

The voltage applied to each of the dimmable windows 14 is controlled byan associated controller 16 using electrical energy produced by anenergy harvesting device 18. The energy harvesting device 18 maycomprise, by way of example and without limitation, a thermoelectricenergy harvesting device that generates electrical power from a thermalgradient on-board the aircraft. For example, a thermoelectric energyharvesting device may be placed between two solid materials of differenttemperatures or between a solid and a fluid at different temperatures togenerate electricity. In the case of aircraft, such surfaces include theaircraft fuselage structure, the aircraft window frame structure, thewindow exterior surface, various window inner panes (including theelectrochromatic dimming surface itself), the sidewall panel and heatsinks that may be placed in air spaces such as the air between the sidewall panel and the insulation blankets or the air spaces between thewindow inner panes. These thermoelectric devices take advantage of thetemperature extremes experienced by the aircraft while cruising at highaltitudes, and to a lesser degree during warm days and nights while onthe ground. A thermoelectric energy harvesting device of the typedescribed above may be integrated into a stringer clip to generateelectricity from the temperature differential across the aircraftinsulation blankets.

Other types of energy harvesting devices 18 are contemplated. Forexample, an energy harvesting device 18 may be employed that convertsradiation into electrical power. One example of such a device is aphotovoltaic device, also known as a solar cell, that converts lightenergy (photons) into electrical power. Sources of light energy nearpassenger windows on aircraft include solar radiation and cabinlighting. The energy harvesting device 18 may comprise a device forconverting motion into electrical power. For example, piezoelectric orelectrodynamic devices may be used to harvest energy, by convertingvibration and motion energy into electricity. Vibration/motion energyexist near passenger windows in the form of aircraft skin vibration,side wall panel vibration and aircraft turbulence motion. It should benoted here that the energy harvesting device 18 may comprise acombination of any of the energy conversion devices discussedimmediately above

As will be discussed in more detail below, the controller 16 isresponsive to dimming adjustment controls operated by a passenger at awindow 14 for controlling the opacity of the window 14 using electricalpower generated by the energy harvester 18. Thus, each of the passengersadjacent one of the windows 14 may independently adjust window opacityusing individual controls. Alternatively, however, one or more of thedimmable windows 14, or all of the dimmable windows 14 may be controlledby a central controller 12 on-board the aircraft, operated by a pilot orcabin attendant. Accordingly, a pilot or cabin attendant may overrideopacity settings selected by passengers so as to fully dim or lightenthe windows 14 in order to prepare the aircraft for landing or takeoff,and for the overall comfort of passengers as where the cabin needs to bedimmed to allow passengers to sleep or view a movie. As will bediscussed later in more detail, the central controller 12 operates thedimmable windows 14 through a wireless data link, thus obviating theneed for wiring to connect the windows 14 to the central controller 12.

FIG. 2 depicts an alternate control system 10 a in which a single energyharvester 18 a is coupled with controllers 16 in order to controlmultiple windows 14.

Another embodiment of the control system 10 b is shown in FIG. 3 whereinmultiple energy harvesters 18 a generate electrical power that is storedin a single energy storage device 22 a. In this embodiment, multipledimmable windows derive power from a single energy storage device 22 awhich may comprise a battery or capacitor, for example.

In still other embodiments, one of the controllers 16 may be used tocontrol more than one of the dimmable windows 14.

Referring now simultaneously to FIGS. 1 4 and 5, each of the controllers16 comprises a control circuit broadly including a first powerconditioning circuit 20, an energy storage device 22, a second powerconditioning circuit 24, a processor 28, a radio transceiver 26 and apair of passenger-operated push button control switches 30 a, 30 b.

The central controller 12 includes a wireless transceiver 15 thatcommunicates with the radio transceiver 26 forming part of each of thecontroller 16. The power conditioning circuit 20 receives energy fromthe energy harvester 18 and functions to condition this energy andtrickle charge the energy storing device 22. A similar powerconditioning circuit 24 maybe used to condition power used by the window14, such as to provide power at specific voltages used to control theopacity of window 14. The processor 28 controls the flow of electricalpower from the storage device 22 to the window 14 using a switchingtransistor 32. The energy storage device 22 may comprise a rechargeablebattery or a super capacitor which receives conditioned power from thepower conditioning circuit 20.

The processor 28 is powered using electrical power stored in the energystorage 22, and operates in any of four modes described below. Theprocessor 28 may comprise a programmed microcontroller such as aParallax BS2pe or a Texas instruments MSP430. The processor 28 may beprogrammed to maintain itself in a low power, “sleep” mode most of thetime so as to draw minimal power from the storage device 22.

The processor 28 is programmed to periodically awaken from the sleepmode to check for broadcast radio communications signal from the centralcontroller 12. When awakened, the processor 28 temporarily powers up theradio transceiver 26 to listen for signals from the transmitter 15. Ifsuch messages are present from the central controller 12, the processor28 responds by carrying out the instructions contained in thetransmitted message. These instructions may include, by way of exampleand without limitation, setting the window 14 to minimum opacity,setting the window 14 to maximum opacity, changing the passenger controlset points or switching into a power down mode. After these instructionshave been carried out, the processor 28 returns to the sleep mode.

The processor 28 may be programmed to awaken from the sleep mode on aperiodic basis, for example every two seconds. In this case, eachbroadcast command from the central controller 12 would be broadcastcontinuously for at least two seconds in order to assure every window 14will be awakened at least once during the duration of the broadcast fromthe central controller 12 and therefore have a chance to receive thecommand. In some embodiments, the control circuit 16 may require severalmilliseconds to check for broadcast messages from the central controller12. It may thus be appreciated that each control circuit 16 remains in alow power sleep mode the majority of the time, and is awakened only tolisten for possible commands from the central controller 12, or responddirectly to a passenger request to change the opacity setting of thewindow 14.

It should be noted here that because the processors 28 in all of thewindows 14 awaken and respond to broadcast commands from centralcontroller 12 at different times (up to two seconds apart in theillustrated example), the processors 28 commence their operations atslightly different times. Because these actions may take several secondsto complete (e.g. transition from minimum to maximum opacity, forexample), the delay in certain windows will not be normally noticeableto passengers, particularly since each window 14 may be transitioningfrom different opacity points which will tend to camouflage the timedisparities between the windows 14.

Each of the processors 28 may also adjust a setting in its memory inresponse to broadcasted commands from the central controller 12 thatrequire the processor 28 to respond in different ways to later inputs atcontrol buttons used by passengers to change opacity settings. Forexample, if the central controller 12 sends a signal to the controlcircuits 16 to indicate that the passenger cabin is switching into anighttime mode to facilitate movie watching or sleeping, a “minimumallowable opacity set point” variable in the memory of the processor 28may be adjusted which later restricts the passenger's control of thewindow to a range of, for example, 95-100% of opacity. This function maybe used, for example, to restrict the range of operation of the window14 to 95-100% opacity (instead of 0-100% opacity) when the cabin crewwishes to configure the cabin to accommodate passenger sleeping or moviewatching, while still allowing some degree of visibility through thewindows 14.

The processor 28 also operates in a passenger control mode, in which theprocessor 28 is programmed to awaken anytime a passenger presses one ofthe passenger control buttons 30 a, 30 b used to change the opacity ofwindow 14. When awakened, the processor 28 begins changing the opacityof window 14 in the direction corresponding to which of the buttons 30a, 30 b has been pressed, until the passenger releases the button oruntil the window 14 has reached a predefined opacity set point, ormaximum or minimum opacity levels. For example, a passenger may press adarken button (e.g. 30 b) twice in order to darken the window 14 two setpoints darker. In this example, the processor 28 may flash an LED 34 (or74 in FIG. 8) adjacent to a symbol on the control interface in order toindicate the target set point while the processor 28 operates to darkenthe window 14 to that selected set point.

Finally, the processor 28 may operate in a power down mode. In responseto a command signal from the central controller 12, the processor 28transitions into a semi-permanent, low power sleep mode or,alternatively may completely shut down. This mode may be entered, forexample, when passenger control of the windows 14 is not necessary ordesired. This mode may be used between flights, for example, anytime theaircraft is powered down, during aircraft overnight storage and/orduring aircraft long term storage. In this mode, very little or no poweris drawn from the energy storage device 22, if the storage device 22continues to be trickle charged by any available energy from the energyharvesting device 18.

The power down mode of the processor 28 may be ended, for example, bypressing both passenger control buttons 30 a, 30 b simultaneously. Theprocessor 28 may then power up the radio transceiver 26 in order tocheck for broadcast commands from the central controller 12. If abroadcast command is received by the radio transceiver 26, the processor28 switches into the airplane control mode and carries out operationsconsistent with the command from central controller 12. If no suchbroadcast command is present from central controller 12, then theprocessor 28 may re-enter the sleep mode. It may thus be appreciatedthat the power down mode for the processor 28 allows the control systemto draw no or minimal power when the dimming function for the window 14is not needed.

Additional techniques may be used to further reduce the powerconsumption of the windows 14 and associated controller 16. For example,the processor 28 may be programmed to apply a short circuit across thewindow 14 in order to drive it toward 0 V in lieu of driving the window14 to or through 0 V by applying an energy-consuming charge to thewindow 14. Also, energy recovery may be employed as the window 14 isdriven toward 0 V, by programming the processor 28 to temporarilyconnect the window 14 to the input side of the first power conditioningcircuit 20.

As shown in FIG. 8, the passenger control buttons 30 a, 30 b may belocated adjacent the window 14, and may comprise momentary membrane pushbuttons in which one of the buttons (30 a) functions to lighten thewindow 14, while the other button 30 b functions to darken the window14. Indicator lights 74 may be optionally provided to provide acontinuous or momentary indication of the opacity of the window 14 orthe target opacity set-point toward which the window 14 is moving. Thepassenger selection buttons 30 a, 30 b allows the passenger to controlwindow capacity in a continuous range or incremental steps.

Referring particularly now to FIG. 5 the processor 28 is powered by fivevolts derived from the storage device 22 and applied to the PWR pin onprocessor 28. As indicated above, the processor 28 typically drawslittle or no current from the storage device 22 while in the sleep modeand even less or no power during the power down mode. When the processor28 periodically awakes, it delivers a signal on pin 8 which turns on theswitching transistor 38, thereby coupling power to the radio transceiver26, and allowing the control circuit 16 to “listen” for commands fromthe central controller 12.

Switches 30 a, 30 b, which are double pole, single throw switches (FIG.5), are connected to pins 1 and 2, respectively of processor 28 and, aspreviously indicated function as passenger controls to control theopacity of window 14. Momentary closure of either switch 30 a or 30 bawakens the processor 28 to commence the passenger control mode. Thepush buttons 30 a, 30 b may have “up” and “down” or “lighten” and“darken” symbols printed on or near them using photoluminescentmaterials to allow viewing in a darkened cabin. When either button 30 aor 30 b is pressed, the processor begins the process of lightening ordarkening the window 14. When the button 30 a, 30 b are released, theprocessor 28 terminates the process of lightening or darkening thewindow 14 and switches back into a sleep mode. Alternatively, pressingone of the buttons 30 a, 30 b may command the processor 28 to change thewindow 14 in preprogrammed opacity increments.

The remaining poles of switches 30 a, 30 b are connected to the resetpin of processor 28 and may be used to awaken the processor 28 from thepower down mode. If desired, LEDs 34 may be used to illuminate membranetype switch buttons 30 a, 30 b when these buttons are pressed, or tovisually indicate which preprogrammed set points to which the processor28 is changing the window. This provides the passenger with visualfeedback that his/her input has been received and is being processed.This feedback is especially useful for electrochromatic dimming windowsthat may respond slowly to changes in passenger settings.

The processor 28 includes memory that allows “learning” the opacitystate of the window by any of several methods. For example, theprocessor 28 may measure the electric charge on the window 14, therebyinferring the opacity of the window 14. Alternatively, as shown in FIG.7, an illuminated diode 68 and a phototransistor 70 may be positioned onopposite sides of the window 14, and cooperate as an opacity sensor. Thesensed opacity may be input to the processor 28 in order to determineand record the current window opacity.

Additional details of portions of the controller 16 are shown in FIG. 6.The energy harvesting device 18 is connected to the control circuit 16by a connector 40. Power from the harvesting device 18 is delivered tothe power conditioning circuit 20 which may comprise a buck-boostconverter that increases the voltage to a desired working level, forexample 2.5V-3.3V in one useful embodiment. The converter may comprise alinear voltage regulator 44 coupled with a synchronous step-up converter46. The conditioned power is delivered through a selector switch 62 to aconnector 64 that is connected with the energy storage device 22 whichmay comprise a nickel metal hydride battery. Power output by theconditioning circuit 20 is also delivered to a step-up converter 48which increases the voltage of the power output by the powerconditioning circuit 20 to a voltage, such as 5 volts that is suitableto power the processor 28 as well as the radio 26 when the output fromthe energy storage device 22 is too low to maintain this required levelof voltage.

The second power conditioning circuit 24 may comprise a voltage limiterwhich is controlled by the processor 28 and functions to limit thevoltage applied to the window 14 to a pre-selected level, for example1.2V in one useful embodiment. A connector 50 couples the processor 28with the previously discussed radio transceiver 26 (FIG. 5). Transistor32 is connected between the voltage limiter 24 and the window 14, andfunctions to limit the current applied to the window 14 based onprogrammed values stored in the processor 28.

The selector switch 62 is an optional item that can be used to switchdelivery of the conditioned power from the harvester device 18 to any ofmultiple batteries or other energy storage devices.

Various other embodiments and variations are possible. For example,other methods may be employed to end the power down mode of theprocessor 28. The power down mode may be ended, for example, by pressingboth passenger control buttons 30 a, 30 b which grounds the reset pin ofthe processor 28. Alternatively, a magnet 37 may be held close to a reedswitch 36 (FIG. 5) which grounds a pin on the processor 28. In responseto either of these pins being grounded, the processor 28 will thenawaken and transition into the aircraft control mode or the sleep mode.This method is advantageous in that the radio transceiver 26 is notrequired to be powered up and the central controller 12 does not need tobroadcast during the time it takes for personnel to awaken all thewindows 14 at each window location.

In another embodiment, the central controller 12 may request each of thewindows 14 to perform a self-check and report back the results. Thisself check, which is performed by each of the processors 28, mayinclude, for example, a complete or summarized usage history and thecurrent state of the energy storage device 22 (e.g. current voltagelevel). The processor 28 may then direct the transceiver 26 to transmitthis status report to the central controller 12. The central controller12 may individually address each of the windows 14 by communicating withthe associated processors 28. Each of the windows 14 may report itsparticular location to the central controller 12 using any of severalknown methods, such as that disclosed in U.S. Pat. No. 7,137,594 issuedNov. 21, 2006, owned by The Boeing Company. To assist in addressingspecific windows 14, each of the controllers 16 may include aprogrammable device that identifies the location of the associatedwindow 14 within a cabin. For example, the controller 16 may include asimple DIP switch (dual in-line package switches) that may be set touniquely identify the location of the window 14. By knowing the locationof the windows 14, the central controller 12 can interrogate or controlspecific windows 14 or groups of windows. For example, the centralcontroller 12 may issue commands dimming all of the windows only in thefirst class section of the aircraft.

It should be noted here that although the illustrated central controller12 and controller 16 each include a transceiver 15, 26 to allow fullduplex communication, in some applications only simplex or one-waycommunication may be needed. Where only one way communication is needed,transceivers are not required. Instead, the central controller 12 mayhave a radio transmitter (not shown) and the controller 16 may have aradio receiver (not shown).

Another embodiment of the power down mode comprises lengthening the timeby which the processor 28 is in the sleep mode, for example to a periodof 10 minutes. In this embodiment, 2 n order to end the power down mode,the central controller 12 would continuously transmit an “awake” messagefor at least 10 minutes. This method would reduce the average powerconsumption of the control system significantly.

Instead of lighten and darken passenger control buttons 30 a, 30 b shownin FIG. 8, two or more buttons 30 c shown in FIG. 7 may be provided,wherein each of the buttons 30 c corresponds to a specific opacitylevel. For example, the four push buttons 30 c shown in FIG. 7 may, forexample, correspond to 0%, 50%, 95% and 100% opacity levels for thewindow 14. In this embodiment, a passenger may for example, press the50% button 30 c. In this event, the processor 28 would then control thedimmable window 14 to a 50% opacity level. The advantage of this methodis that the passenger only has to press the button momentarily and doesnot have to hold the button down until the desired opacity level isachieved. This embodiment is especially useful in connection withdimmable windows 14 that change slowly in opacity. Various other formsof passenger interface controls are possible, including toggling thetarget set point up or down on a scale of several predefined set points.

The central controller 12 may also send other commands to the window'scontroller 16. For example, the processor 28 may be commanded to changethe color of the window 14 or to reveal an image in the window 14. Theprocessor 28 may also be programmed to restrict the frequency ofpassenger interaction. For example, if the processor 28 detects that thepassenger is activating the window 14 excessively, the processor 28 mayinitiate a “time out” mode wherein it will cease responding to allpassenger commands for a set period of time, or may adjust the windowopacity more slowly. The processor 28 may also monitor the voltage inthe energy storage device 22 and initiate “time out” modes or sloweropacity changes or initiate other energy saving modes, such as onlyresponding to commands from the central controller 12.

Various photoluminescent materials may be applied or incorporated intothe passenger control buttons 30 a, 30 b, 30 c which respond tonon-visible light sources. These non-visible light sources, such asultraviolet light, may be included in the cabin interior lighting of theaircraft such that, even when cabin lights are turned down, thisnon-visible light source is present to illuminate the photoluminescentmarkings on the passenger control buttons 30 a, 30 b, 30 c, thus makingthem visible in a darkened cabin.

Although the embodiments of this disclosure have been described withrespect to certain exemplary embodiments, it is to be understood thatthe specific embodiments are for purposes of illustration and notlimitation, as other variations will occur to those of skill in the art.For example, although the dimmable window system has been disclosed inconnection with its application to aircraft, the system can be employedin other types of vehicles and in stationary applications such as inbuildings.

1. A dimmable window system, comprising: at least one window havingelectrically controllable opacity; an electrical power storage devicefor supplying electrical power used to control the opacity of thewindow; and, a control circuit coupled with the window and the storagedevice for controlling the opacity of the window.
 2. The dimmable windowsystem of claim 1, further comprising a device coupled with the storagedevice for harvesting energy and converting the harvested energy toelectrical power.
 3. The dimmable window system of claim 2, wherein theenergy harvesting device includes any of: a device for converting atemperature gradient to electrical power, a device for converting motioninto electrical power, a device for converting radiation into electricalpower.
 4. The dimmable window system of claim 3, wherein the device forconverting radiation into electrical power includes a photovoltaicdevice for converting light into electrical power.
 5. The dimmablewindow system of claim 2, wherein the control circuit includes a powerconditioning circuit for conditioning electrical power from the energyharvesting device before the electrical power is stored in the storagedevice.
 6. The dimmable window system of claim 1, wherein the electricalpower storage device is one of: a capacitor, and a battery.
 7. Thesystem of claim 1, wherein the control circuit includes a powerconditioning circuit for conditioning the electrical power drawn fromthe power storage device to control the opacity of the window.
 8. Thedimmable window system of claim 1, wherein the control circuit includesa window dimming adjustment control for selecting a level of opacity ofthe window.
 9. The dimmable window system of claim 1, wherein thecontrol circuit includes a microcontroller responsive to the operationof the window dimming adjustment control for altering the electricalpower applied to the window.
 10. The dimmable window system of claim 9,wherein the microcontroller includes a power saving sleep state, and anawake state initiated by the operation of the window dimming adjustment.11. The dimmable window system of claim 1, wherein the control circuitincludes: a first dimming control producing control signals forselecting the level of opacity of the window, a wireless radiotransmitter for transmitting the control signals from the first dimmingcontrol to the window, a radio receiver at the window for receiving thecontrol signals from the transmitter, and a processor responsive to thecontrol signals for controlling the opacity of the window.
 12. Thedimmable window system of claim 11, wherein the control circuit includesa second dimming control at the window, the second dimming control beingcoupled with the processor and operative for selecting the level ofopacity of the window.
 13. The dimmable window system of claim 1,wherein the control circuit includes means for sensing the level ofopacity of the window.
 14. The dimmable window system of claim 1,wherein the control circuit includes a photoluminescent window dimmingadjustment control for selecting a level of opacity of the associatedwindow.
 15. A dimmable window system for vehicles, comprising: aplurality of windows on a vehicle, each of the windows havingelectrically controllable opacity; at least one energy harvesting devicefor harvesting energy on-board the vehicle and generating electricalpower; storage means for storing electrical power generated by theharvesting device; and, a plurality of control circuits respectivelycoupled with the windows, each of the control circuits being coupledwith the storage means and operative for controlling the opacity of theassociated window using electrical power from the storage means.
 16. Thedimmable window system of claim 15, further comprising: a controlleron-board the vehicle for generating control signals used to remotelycontrol the opacity of at least certain of the windows; and, a wirelesscommunication link between the controller and the control circuitsassociated with the certain windows, the communication link beingoperative for delivering the control signals to the control circuitsassociated with the certain windows.
 17. The dimmable window system ofclaim 15, wherein each of the control circuits includes: a windowdimming adjustment control for selecting a level of opacity of theassociated window, and a processor responsive to the adjustment controlfor controlling the delivery of electrical power from the storage meansto the window.
 18. The dimmable window system of claim 15, wherein theenergy harvesting device includes any of: a device for converting atemperature gradient to electrical power, a device for converting motioninto electrical power, a device for converting radiation into electricalpower.
 19. The dimmable window system of claim 18, wherein the devicefor converting radiation into electrical power includes a photovoltaicdevice for converting light into electrical power.
 20. The dimmablewindow system of claim 15, wherein each of the control circuits includesa power conditioning circuit for conditioning electrical power from theenergy harvesting device before the electrical power is stored in thestorage means.
 21. The dimmable window system of claim 15 wherein thestorage means is one of: a capacitor, and a battery.
 22. The dimmablewindow system of claim 15, wherein each of the control circuits includesa window dimming adjustment control for selecting a level of opacity ofthe associated window.
 23. The dimmable window system of claim 22wherein the dimming adjustment control include a photoluminescentmaterial allowing the adjustment control to be visible under lowlighting conditions.
 24. The dimmable window system of claim 22, whereineach of the control circuits includes a microcontroller responsive tothe operation of the window dimming adjustment control for altering theelectrical power applied to the window.
 25. The dimmable window systemof claim 24, wherein the microcontroller includes a power saving sleepstate, and an awake state initiated by the operation of the windowdimming adjustment.
 26. The dimmable window system of claim 16, whereinthe wireless communication link includes: a radio transmitter fortransmitting the control signals, a radio receiver at each of thewindows for receiving the control signals from the transmitter.
 27. Thedimmable window system of claim 15, wherein the control circuit includesmeans for sensing the level of opacity of the window.
 28. A method ofcontrolling electrically dimmable windows on-board an aircraft,comprising the steps of: (A) harvesting energy on-board the aircraft;(B) storing the energy harvested in step (A) as electrical power; and,(C) using the electrical power stored in step (B) to control the opacityof the windows.
 29. The method of claim 28, wherein step (A) isperformed by any of— converting a temperature gradient into electricalpower, converting motion into electrical power, converting radiationinto electrical power.
 30. The method of claim 29, wherein convertingradiation into electrical power includes converting light intoelectrical power.
 31. The method of claim 28, wherein step (B) includesstoring the electrical power in a battery.
 32. The method of claim 28,wherein step (B) includes storing the electrical power in an electricalcapacitor.
 33. The method of claim 28, further comprising the steps of:(D) controlling the opacity of the windows from a central controllocation.
 34. The method of claim 33, wherein step (D) is performedusing a wireless data link.
 35. The method of claim 33, wherein step (D)includes powering a radio receiver forming part of the wireless datalink using electrical power stored in step (B).
 36. The method of claim28, wherein step (C) includes: using a processor to control the amountof stored electrical power that is used to control the opacity of thewindow, placing the processor in an inactive, sleep mode, periodicallyawaking the processor from the sleep mode to receive signals commandingthe processor to change the amount of stored power delivered to thewindow.